Many systems of electrical devices, such as computer and communication equipment, require continuous, uninterrupted, quality power. Many major data centers are currently working toward operating continuously twenty-four hours a day, seven days a week without shutdowns for maintenance or repairs. Such centers often contain many different computer systems which can have hundreds, even thousands of unique branch electrical circuits distributing power to interrelated, critical electrical devices. A power failure or even disturbance in just one branch circuit can disable the entire data center and result in hours of lost time while computer systems are restored and data recovered.
Previous power protection schemes have focused either on providing an uninterruptible source of power, or on providing redundancy within individual computer elements. Despite having 3 potential power sources (commercial utility power, generators, and batteries), uninterruptible power supplies (UPS) can and do fail with distressing frequency. Even if the UPS is totally successful in providing a source of uninterruptible power, it provides no protection if an electrical problem occurs after power has left the UPS's output bus.
At the ends of the hundreds of individual power distribution branch circuits that make up a complex computer system, attempts have been made to provide multiple power supplies with elaborate means for switching supplies as quickly as possible upon detection of a fault, such as an undervoltage situation or an internal power supply failure. Such approaches also can include battery backup for limited time operation in case of an input power failure. Previous patents cover a number of alternatives for how internal power supply redundancy and/or batteries can be employed, but such systems are supplied by a common path back to a common power source. Since power must continuously be fed through such commonalities, a failure in a portion of the power path or in the source of power will shutdown the entire system. Furthermore, these continuously powered portions can never be removed from service for maintenance or modification which is unacceptable if non-stop computer operation is to be achieved.
To summarize the current state of the art: 1. UPS systems by themselves are not sufficiently reliable to provide truly uninterrupted power. 2. UPS systems provide no or limited protection from short circuits, circuit breaker failures, wire failures, transformer failures, plug, receptacle or connection failures, load induced failures and problems, human error, or other problems that typically occur after conditioned power leaves the UPS output bus. 3. Current systems for delivering power to branch circuits follow a single path which can not be taken out of service for maintenance, repair, or modification without powering down the dependent equipment. 4. While the equipments powered by the branch circuits contain a growing sophistication of internal power supply redundancy, these power supplies are ultimately connected to a single power source via a single input power cord or hardwired power path.